Ferrite core coil device, sensor device for determining rotational speed of a rotatable object with such a ferrite core coil device and turbocharger with such a sensor device

Abstract

A ferrite core coil device as a sensing element for a sensor device determining a rotational speed of a metallic rotatable object includes a coil having a first sector and a second sector and a ferrite core holding the coil. The ferrite core has a shape of a disk lacking a disk sector and defined by a contour of the disk and a chord of the disk. The chord forms a bending edge of the ferrite core. The first sector of the coil is not arranged on a bed of the ferrite core and the second sector of the coil is arranged on the bed. The first sector is bent around the bending edge at a bending angle with respect to the second sector.

What is claimed is: 
     
       1. A ferrite core coil device as a sensing element for a sensor device determining a rotational speed of a metallic rotatable object, comprising:
 a coil having a first sector and a second sector; and 
 a ferrite core holding the coil, the ferrite core has a shape of a disk lacking a disk sector and defined by a contour of the disk and a chord of the disk, the chord forms a bending edge of the ferrite core, the first sector of the coil is not arranged on a bed of the ferrite core and the second sector of the coil is arranged on the bed, the first sector is bent around the bending edge at a bending angle with respect to the second sector. 
 
     
     
       2. The ferrite core coil device of  claim 1 , wherein the ferrite core has a pin protruding from the bed, the pin has a same axis as the ferrite core. 
     
     
       3. The ferrite core coil device of  claim 2 , wherein the coil is wound around the pin. 
     
     
       4. The ferrite core coil device of  claim 2 , wherein the bed is delimited by a supporting edge wall of the ferrite core extending along the contour of the disk and by the bending edge. 
     
     
       5. The ferrite core coil device of  claim 4 , wherein the pin has substantially a same height from the bed as the supporting edge wall. 
     
     
       6. The ferrite core coil device of  claim 1 , wherein a radius of the coil is smaller than a radius of the ferrite core. 
     
     
       7. The ferrite core coil device of  claim 1 , wherein a ratio between the first sector of the coil and the second sector of the coil is between 1:1 and 1.5:1. 
     
     
       8. The ferrite core coil device of  claim 1 , wherein the bending angle is between 70 and 110 degrees. 
     
     
       9. The ferrite core coil device of  claim 8 , wherein the coil is a substantially L-shaped coil with a bending angle of 90°. 
     
     
       10. The ferrite core coil device of  claim 1 , wherein the coil has between ten and thirty windings. 
     
     
       11. The ferrite core coil device of  claim 1 , wherein the coil has a plurality of windings each in contact with the bed. 
     
     
       12. The ferrite core coil device of  claim 1 , wherein the coil is printed on a flexible polymer substrate. 
     
     
       13. The ferrite core coil device of  claim 1 , wherein the ferrite core has a thickness between 0.2 mm and 2 mm. 
     
     
       14. The ferrite core coil device of  claim 1 , wherein the ferrite core has a relative permeability between 50 and 3000. 
     
     
       15. A sensor device for determining rotational speed of a rotatable object, comprising:
 a sensor segment; 
 a mounting segment; 
 a connector segment; and 
 a ferrite core coil device arranged at a sensor tip of the sensor segment, the ferrite core coil device including a coil having a first sector and a second sector and a ferrite core holding the coil, the ferrite core has a shape of a disk lacking a disk sector and defined by a contour of the disk and a chord of the disk, the chord forms a bending edge of the ferrite core, the first sector of the coil is not arranged on a bed of the ferrite core and the second sector of the coil is arranged on the bed, the first sector is bent around the bending edge at a bending angle with respect to the second sector. 
 
     
     
       16. A turbocharger, comprising:
 a turbocharger housing; 
 a compressor impeller arranged in the turbocharger housing; and 
 a sensor device including a sensor segment, a mounting segment, a connector segment, and a ferrite core coil device arranged at a sensor tip of the sensor segment, the ferrite core coil device including a coil having a first sector and a second sector and a ferrite core holding the coil, the ferrite core has a shape of a disk lacking a disk sector and defined by a contour of the disk and a chord of the disk, the chord forms a bending edge of the ferrite core, the first sector of the coil is not arranged on a bed of the ferrite core and the second sector of the coil is arranged on the bed, the first sector is bent around the bending edge at a bending angle with respect to the second sector, the sensor segment is arranged in a wall of the turbocharger housing that has a recess, the ferrite core coil device protrudes through the wall and faces the compressor impeller at a predefined distance from the compressor impeller. 
 
     
     
       17. The turbocharger of  claim 16 , wherein the predefined distance is between 0.5 and 1 mm. 
     
     
       18. A method for determining a rotational speed of a rotatable object, comprising:
 providing a sensor device including a sensor segment, a mounting segment, a connector segment, and a ferrite core coil device arranged at a sensor tip of the sensor segment, the ferrite core coil device including a coil having a first sector and a second sector and a ferrite core holding the coil, the ferrite core has a shape of a disk lacking a disk sector and defined by a contour of the disk and a chord of the disk, the chord forms a bending edge of the ferrite core, the first sector of the coil is not arranged on a bed of the ferrite core and the second sector of the coil is arranged on the bed, the first sector is bent around the bending edge at a bending angle with respect to the second sector; 
 placing the sensor device with the sensor tip at a predefined distance from the rotatable object; 
 applying an electrical input current to the ferrite core coil device; 
 reading an amplitude modulated output voltage signal output from the sensor device; and 
 determining the rotational speed by evaluating a demodulated output voltage signal of the sensor device.